Contemporary consumer electronic devices including portable computing devices such as mobile phones and tablet computers, for example, can have glass screens that occupy a substantial portion of at least one surface of the device. Since these devices can be designed to be handheld, the glass screen can be exposed to a variety of environmental factors that can break or crack the glass screen. To reduce the risk of damage to the glass screen, device manufacturers can make the screens using glass that is strengthened or tempered chemically or thermally.